Russia had fought
bravely for the Allies at the beginning of the war, but
about the time the United States entered, a revolution
drove the Czar from his throne. Russia was so upset by
the revolution that after a year it gave up trying to keep its army at the front, and made peace with Germany. . Hundreds of thousands of German soldiers were thus left effort free to attack the Allies in the west. Germany thought that
if she could succeed in taking Paris before many Americans
arrived in the trenches, the war would be won. It was
her last chance to win.